JP2000319329A - Production of rubber latex - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a rubber latex composed chiefly of butadiene and having a large particle diameter in a short time. SOLUTION: This method for producing in a short time a rubber latex with a particle diameter of >=0.1 μm in the process for producing a synthetic rubber composed chiefly of butadiene through emulsion polymerization comprises adding an electrolyte having the ability to flocculate rubber latex particles to the polymerization system at a point when a polymerization conversion rate comes to 10-70 wt.% in the middle of the polymerization reaction so as to generate no flocculates as a by-product in the polymerization process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a rubber latex capable of stably producing a large particle size rubber latex in a short time.

[0002]

2. Description of the Related Art Rubber latex containing an aliphatic conjugated diene as a main component is used as a tire or as a graft polymer in ABS.
Resin (acrylonitrile, butadiene, styrene), M
It is used for various purposes such as BS resin (methyl methacrylate / butadiene / styrene) and high impact polystyrene, and is known to be used mainly for the purpose of improving impact resistance. It is also known that the larger the rubber latex particles, the better the impact resistance. By the way, when rubber latex is produced by an emulsion polymerization method, there is a clear relationship between the time required for polymerization and the particle size of the rubber latex, and it is well known that it takes a long time to obtain a rubber latex having a large particle size. ing. Therefore, development of a production method for obtaining large rubber latex particles in a short time is desired.

As a method of obtaining a rubber latex having a large particle size, a method of mechanically aggregating particles of a small particle size latex produced in advance to increase the size (Japanese Patent Publication No. 3-54983).
Publication), but there is a possibility that an unnecessary repellent may be generated at the time of aggregation. Further, a special device is required, operability is poor, and there are many disadvantages.

In addition, there is a technique of adding an electrolyte to a small particle size latex produced in advance to coagulate and enlarge particles (Japanese Patent Application Laid-Open No. 9-104715). However, a coagulation step is required in addition to a polymerization step. After the coagulation, an operation such as raising the pH with an alkali substance and re-stabilizing the latex is required, which is complicated and lowers the productivity.

[0005] There is a method for producing a rubber latex in which an electrolyte is added to a polymerization system before the start of polymerization (JP-A-10-77317, JP-A-56-136807, etc.). In order to obtain a rubber latex having a particle diameter of 0.26 to 0.5 μm, as in the case of simply polymerizing a large-diameter rubber latex, in order to adjust the size of latex particles by adding an electrolyte from the initial stage of polymerization, Very long, 50-92 hours,
Poor productivity. Since the addition of the electrolyte of the present invention is after the initiation of the polymerization reaction, the timing of addition is clearly different.

As a method of coagulating and expanding particles during polymerization, a rubber latex having a small particle size prepared separately is added to a polymerization system (JP-B-48-16060, JP-A-63-48313). Or a method in which a monomer is additionally added to the polymerization system during the polymerization to effect polymerization (Japanese Patent Publication No. 3-21).
No. 65). In order to enlarge the rubber latex particles, it is necessary to add a rubber latex or a monomer having a small particle diameter during the polymerization, but it takes 50 to 60 hours to obtain a particle diameter of 0.25 to 0.45 μm. Cost and low productivity.

As a method for obtaining a rubber latex having a large particle diameter in a short time, a technique of using a small amount of an emulsifier and a vinyl cyanide monomer before the start of polymerization, or a technique of using a small amount of an emulsifier and acetonitrile, propionitrile, butyronitrile, etc. There is a technique using an organic solvent at a polymerization conversion of 20% by weight or less, which accelerates the polymerization reaction. Further, a technique for obtaining a rubber latex having a large particle diameter by continuously adding an emulsifier when the polymerization conversion reaches 10 to 70% by weight (Japanese Patent Laid-Open Publication No.
17508 and JP-A-8-27227). This technology utilizes the phenomenon that the particle coverage of the particle surface with the emulsifier decreases as the particles grow and the rubber latex becomes unstable, causing the particles to fuse and coalesce. It is a method of adjusting the diameter enlargement. Even in the technology for producing these rubber latexes, to obtain rubber latex having a particle size of about 0.3 μm, 30
It takes time and productivity is low.

[0008]

At present, it takes a long time to produce rubber latex having a large particle diameter. Also,
In the method of obtaining a rubber latex with a small particle diameter, adding a flocculant and coagulating and expanding the particles to obtain a rubber latex with a large particle diameter, a coagulation step is required, and operations such as coagulation operation and re-stabilization of the latex are performed. However, there are many disadvantages, such as troublesomeness and easy generation of repellents. In addition, the technique of enlarging particles during the polymerization reaction results in a longer polymerization reaction time and lower productivity. The present invention has been made in view of the above circumstances, and has as its object to provide a method for producing a rubber latex having a large particle size in a shorter time and without producing by-products.

[0009]

There is a relationship between the particle size of the rubber latex and the polymerization reaction speed, and the polymerization speed generally decreases with a large particle size. For this reason, the present inventors first started the polymerization by a method of obtaining a rubber latex having a particle diameter with a sufficiently high polymerization rate, and at a polymerization conversion of 10 to 70% by weight during the polymerization,
A method of obtaining a rubber latex having a large particle diameter of 0.1 μm or more by causing the particles to coagulate and enlarge by adding an electrolyte and causing the polymerization conversion to react at 80% by weight or more.
In the present invention, a rubber latex having a large particle diameter is used for a short time (6-1 to 1).
4 hours), which is an industrially advantageous production method.

That is, the present invention relates to a monomer comprising an aliphatic conjugated diene monomer, or an aliphatic conjugated diene monomer and an ethylenically unsaturated monomer copolymerizable therewith. In a method for producing a rubber latex by emulsion-polymerizing a monomer in which the proportion of an aliphatic conjugated diene monomer in the monomer is 70% by weight or more, the polymerization conversion rate during the polymerization reaction is 1
A method for producing a rubber latex, characterized in that an electrolyte is added in a range of 0 to 70% by weight (claim 1), wherein the electrolyte is a carboxyl group-containing acid having 6 or less carbon atoms or a salt thereof, or sulfuric acid; The method for producing a rubber latex according to claim 1, which is sodium alone or a mixture of two or more kinds thereof, wherein the electrolyte is an aliphatic conjugated diene monomer or an aliphatic conjugated diene monomer and 3. An amount of 0.1 to 5 parts by weight, based on 100 parts by weight of a monomer containing an ethylenically unsaturated monomer copolymerizable with water.
(Claim 3), and 100 parts by weight of an aliphatic conjugated diene monomer or a monomer containing an aliphatic conjugated diene monomer and an ethylenically unsaturated monomer copolymerizable therewith. Water is used in an amount of 60 to 200 parts by weight, based on 100 parts by weight of the monomer, wherein the proportion of the aliphatic conjugated diene monomer in all the monomers is 70% by weight or more. A method for producing the rubber latex according to the item 2 or 3 (claim 4) is included.

[0011]

In the present invention, first, 100 parts by weight of an aliphatic conjugated diene monomer or a mixture containing an aliphatic conjugated diene monomer and an ethylenically unsaturated monomer copolymerizable therewith is used. 100 parts by weight of a monomer, wherein the proportion of the aliphatic conjugated diene monomer in the total monomer is 70% by weight or more, and preferably 60 to 200 parts by weight of water, more preferably The emulsion polymerization is started in the presence of 70 to 150 parts by weight. The reaction temperature is 30 ° C or higher, preferably 35 ° C to 80 ° C, more preferably 40 ° C to 60 ° C.
It is.

Examples of the aliphatic conjugated diene monomer used in the present invention include 1,3-butadiene, isoprene and chloroprene, and 1,3-butadiene is particularly preferred.

Examples of the ethylenically unsaturated monomer used in the present invention include various vinyl compounds and olefinic compounds. Particularly, methacrylates (eg, methyl methacrylate, ethyl methacrylate, etc.), acrylates ( For example, methyl acrylate, ethyl acrylate, etc.), aromatic vinyl (for example, styrene,
Suitable are α-methylstyrene, etc., or their nuclear-substituted derivatives (eg, vinyltoluene, chlorostyrene, etc.). These are used alone or in a mixture of two or more.

The proportion of the aliphatic conjugated diene monomer in the total monomer including the aliphatic conjugated diene monomer and the ethylenically unsaturated monomer copolymerizable therewith is 70% by weight or more. If the amount is less than% by weight, the properties of the polymer as a rubber are too small, and the toughness cannot be obtained.

Examples of the polymerization initiator used in the present invention include water-soluble persulfuric acid such as potassium persulfate, sodium persulfate and ammonium persulfate, and peroxides such as hydrogen peroxide, cumene hydroperoxide and paramenthane hydroperoxide. A redox initiator as one component can be used.

The amount of the emulsifier used is preferably 1 to 4 parts by weight based on 100 parts by weight of the total monomers. An emulsifier may be added during polymerization in order to keep the particles from fusing with each other or generating repellent due to lack of the emulsifier on the surface of the particles. The emulsifiers used are those used in ordinary rubber polymerization, such as fatty acid soaps such as sodium oleate, or resin acid soaps such as disproportionated potassium rosinate, sodium lauryl sulfate, dodecylbenzene sulfonic acid. An example is soda.

The use of additives such as a chain transfer agent such as mercaptan and a cross-linking agent such as allyl methacrylate is not limited at all.

After the initiation of the polymerization, for example, formic acid, acetic acid, propionate and the like are used as electrolytes having a power to agglomerate the polymer particles within a polymerization conversion range of 10 to 70% by weight, preferably 20 to 60% by weight. Acid, oxalic acid, succinic acid, malic acid, acid having 6 or less carbon atoms containing a carboxyl group such as citric acid or a salt thereof, or a mixture of two or more of these alone or sodium sulfate,
In the form of an aqueous solution of 1 to 20% by weight, 0.1 to 5 parts by weight of an electrolyte is added as a solid content to 100 parts by weight of all monomers,
Agglomeration of latex particles is performed. Polymerization conversion rate is 10
If the amount is less than the weight percentage, repellents are likely to be generated, which is a problem in operation. On the other hand, when the polymerization conversion exceeds 70% by weight, the viscosity of the rubber latex becomes too high, and it becomes difficult to control the temperature and mix and stir. Further, when the amount of the electrolyte to be added is less than 0.1 part by weight, the latex particles cannot be coagulated and enlarged to 0.1 μm or more. Become.

Here, the polymerization conversion (% by weight) is a value determined by the following equation.

[0020]

(Equation 1)

The solid content concentration in the formula is determined by the following method. About 1 g of latex is sampled from a polymerization machine into a pre-weighed ointment can (weight A). Atmospheric pressure (760
(mmHg) until the latex no longer foams and weigh (weight B). After drying in an oven maintained at 120 ° C. for 1 hour, the sample is weighed (weight C).

The value of the solid concentration is determined by the following equation.

[0023]

(Equation 2)

After the addition of the electrolyte, the rubber latex having a particle size of 0.1 μm or more can be obtained in 6 to 14 hours by mixing and stirring until the polymerization conversion becomes 80% by weight or more.
The particles can be made large so that the viscosity of the rubber latex can be handled, and the degree of coagulation and enlargement of the particles can be controlled by increasing the number of electrolytes added during the polymerization. At this time, the repellent in the rubber polymerization step is 0.2% by weight or less.

The rubber latex produced according to the present invention can be used as a synthetic rubber in tires or by graft polymerization to be used in ABS resins, MBS resins and the like.

[0026]

The present invention will be described below with reference to examples.
Note that the present invention is not limited to those described in the examples. Table 1 shows the results of the examples.

Example 1 A pressure-resistant polymerization machine having an internal volume of 3 L whose inside was evacuated to a vacuum,
Per 100 parts by weight of 3-butadiene, 2.0 parts by weight of semi-hardened potassium tallow fatty acid, 0.44 of tripotassium phosphate
Parts by weight, 0.2 parts by weight of n-dodecyl mercaptan, 0.0014 parts by weight of ferrous sulfate, ethylenediamine 4
0.0023 parts by weight of acetic acid disodium, 0.2 parts by weight of sodium sulfoxylate / formaldehyde and 77 parts by weight of pure water are added, mixed, stirred, and heated to 40 ° C. After reaching a predetermined temperature, 0.05 part by weight of paramenthane hydroperoxide is added to initiate a polymerization reaction. After 4.5 hours, when the solid content concentration (SC) was 36.8% by weight and the polymerization conversion was 46.2% by weight, 0.74 part by weight of sodium sulfate was added to the polymerization system. S for 13 hours
C46.3% by weight, polymerization conversion rate 80.7% by weight, particle size 0.118 μm, repellent 0.10% by weight. The value of the repellent represents the ratio of the weight of the repellant to the total monomer weight in percentage.

The obtained rubber latex was coagulated with sodium chloride to prepare a rubber crumb, and the gel content was measured. The result was 87.8% by weight, and the quality was equivalent to that of a rubber latex which was not enlarged during polymerization. .

The gel content is the percentage of the gel in the solid content expressed as a percentage. To determine the percentage of gel, about 5 g
Is coagulated and vacuum dried at 50 ° C. for 48 hours. The solid (about 0.5 g) is put into a 150 mesh wire net (weight A) weighed in advance, weighed (weight B), and immersed in toluene for 48 hours. The gel remaining on the wire mesh is dried at 105 ° C. for 30 minutes and weighed (weight C).
The gel content was calculated by the following equation.

[0030]

(Equation 3)

Example 2 In the same manner as in Example 1, 4.5 hours after the start of polymerization, S
At the time when C was 35.9% by weight and the polymerization conversion was 44.2% by weight, it was changed to add 2.94 parts by weight of sodium sulfate. 134.1 hours SC44.1% by weight, polymerization conversion 8
0.8% by weight, particle size 0.257 μm, repellent 0.12
% By weight.

Example 3 In the same manner as in Example 1, 4.5 hours after the start of polymerization,
The electrolyte to be added was changed to 0.56 parts by weight of oxalic acid at a C of 34.2% by weight and a polymerization conversion of 42.5% by weight. 12
In terms of time, SC was 47.7% by weight, the polymerization conversion was 92.9% by weight, the particle size was 0.102 μm, and the reject was 0.19% by weight.

Example 4 In the same manner as in Example 1, the polymerization temperature was changed to 60 ° C., and 3 hours after the start of the polymerization, at 42.5% by weight of SC and 66.3% by weight of the polymerization conversion, sodium sulfate was added. .74 parts by weight. In 8 hours, SC 47.7% by weight, polymerization conversion 92.9% by weight, particle size 0.130μ
m, 0.20% by weight of repellent. The gel content is 88.9
% By weight, and the quality was equivalent to that of a rubber latex that did not undergo enlargement during polymerization.

Example 5 In the same manner as in Example 1, 6 hours after the start of polymerization,
At the time of 4.6% by weight and the polymerization conversion rate of 69.3% by weight, it was changed so that 0.74 part by weight of sodium sulfate was added. In 12 hours, SC was 48.5% by weight and the polymerization conversion was 88.
The content was 7% by weight, the particle diameter was 0.120 μm, and the repellent was 0.15% by weight.

Example 6 In the same manner as in Example 1, 3 hours after the start of polymerization, SC3 was added.
At the time of 4.6% by weight and the polymerization conversion rate of 41.5% by weight, it was changed to add 0.74 parts by weight of sodium sulfate. In 12 hours, 47.4% by weight of SC and a polymerization conversion of 84.
The content was 5% by weight, the particle size was 0.117 μm, and the repellent was 0.19% by weight.

Example 7 Pure water was changed to 172 parts by weight in the same manner as in Example 1,
Six hours after the start of the polymerization, 2.05 parts by weight of sodium sulfate was added at the time of 28.5% by weight of SC and a conversion of 64.7% by weight. SC34.
8% by weight, polymerization conversion 88.8% by weight, particle diameter 0.10
7 μm, 0.02% by weight of repellents.

COMPARATIVE EXAMPLE 1 When no electrolyte was added during the polymerization according to the method of Example 1, SC was 49.3% by weight, the polymerization conversion was 86.5% by weight,
The particle size was 0.084 μm, and the repellent was 0.12% by weight.
The gel fraction was 88.9% by weight. The viscosity of the latex was 20 poise at 40 ° C., which was a high viscosity that was difficult to handle by ordinary handling.

COMPARATIVE EXAMPLE 2 In the same manner as in Example 1, before the start of the polymerization, sodium sulfate 0.7
It was changed to add 4 parts by weight. The polymerization rate became slow, and at 12 hours, 44.6% by weight of SC and a polymerization conversion rate of 7
It was 3.5% by weight. The repellent increased to 0.32% by weight.

Comparative Example 3 In the same manner as in Example 1, one hour after the start of polymerization,
At 4.3% by weight and at a polymerization conversion of 9.9% by weight, 0.74 part by weight of sodium sulfate was added. 12
In terms of time, SC was 46.1% by weight, the polymerization conversion was 80.0% by weight, and the particle size was 0.097 μm. The amount increased to 1.04% by weight.

Comparative Example 4 Pure water 13 per 100 parts by weight of 1,3-butadiene
0 parts by weight, 0.18 part of semi-hardened tallow fatty acid potassium, β
0.18 parts by weight of sodium salt of a naphthalenesulfonic acid formalin condensate, 0.063 parts by weight of sodium hydroxide,
0.3 parts by weight of n-dodecyl mercaptan and 0.18 parts by weight of potassium persulfate were charged into a 3 L pressure-resistant polymerization machine, mixed with stirring, and heated to 65 ° C. SC20.6 after 12 hours
% By weight, and the polymerization conversion was 35.2% by weight. 3 more
In 8 hours, SC was 43.2% by weight, the polymerization conversion was 96.5% by weight, the particle size was 0.200 μm, and the repellent was 0.20% by weight.

[0041]

[Table 1]

[0042]

According to the method of the present invention, rubber latex having a particle size of 0.1 μm or more can be produced in a short time of 6 to 14 hours, and there is an effect that a by-product is hardly produced as a by-product. The polymerization time can be remarkably shortened as compared with a method for producing a rubber latex having a large particle diameter in which an electrolyte is added before the start of the polymerization reaction.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Toragoro Mitani 829-4 Sonecho, Takasago-shi, Hyogo F-term (reference) 4J011 KA29 KB07 KB08 KB14 4J100 AB02Q AB03Q AB04Q AB08Q AL03Q AS02P AS03P AS07P CA01 CA04 EA09 FA02 FA20 JA29

Claims (4)

[Claims] 1. A monomer containing an aliphatic conjugated diene monomer, or an aliphatic conjugated diene monomer and an ethylenically unsaturated monomer copolymerizable therewith, which accounts for all monomers. In a method for producing a rubber latex by emulsion-polymerizing a monomer having a proportion of an aliphatic conjugated diene monomer of 70% by weight or more, an electrolyte is added in a polymerization conversion rate of 10 to 70% by weight during a polymerization reaction. A method for producing a rubber latex, characterized in that: 2. The method for producing a rubber latex according to claim 1, wherein the electrolyte is an acid having a carboxyl group and having 6 or less carbon atoms or a salt thereof, or sodium sulfate alone or a mixture of two or more thereof. 3. The method according to claim 1, wherein the electrolyte is used in an amount of 100 parts by weight of an aliphatic conjugated diene monomer or a monomer containing an aliphatic conjugated diene monomer and an ethylenically unsaturated monomer copolymerizable therewith. 3. The composition according to claim 1, wherein 0.1 to 5 parts by weight are added.
A method for producing the rubber latex described above. 4. An aliphatic conjugated diene monomer 100 parts by weight,
Or a monomer containing an aliphatic conjugated diene monomer and an ethylenically unsaturated monomer copolymerizable therewith, wherein the proportion of the aliphatic conjugated diene monomer in all the monomers is 70% by weight. With respect to 100 parts by weight of the above monomer, water is added in an amount of 60 to
4. The method for producing a rubber latex according to claim 1, wherein 200 parts by weight are used.